Abstract: Demographic information is often an important component of a health survey because a disease or a health behavior may likely be associated with some demographic variables. For example, one study found that the smoking prevalence rate dramatically increases for 15 to 16 year old adolescents.1 When ethnic differences were examined, the study also found that Black adolescents have significantly lower prevalence rate and tend to initiate smoking later than do their white counterparts.1 Attempting to validate self-report smoking data with biochemical indicators as a comparison standard for adolescents 12 to 14 years old, researchers found that Blacks were more likely than whites to underreport cigarette smoking and tobacco use.2 All these findings suggest that without examining some demographic factors, we may not get a full picture of the prevalence of adolescent smoking. Examining demographic differences can help researchers better understand the phenomenon and develop health-promotion and disease-prevention activities accordingly. Furthermore, if researchers can standardize these demographics, it is likely that results of similar studies can be compared from study to study. The purpose of this research note is to provide readers with the commonly adopted demographic categorizations and their estimates from national sources (e.g., U.S. Department of Commerce, U.S. Department of Health and Human Services).